Flare tip having internal spin vanes

ABSTRACT

A flare tip for the burning and disposal of combustible waste gases including internal spin vanes is provided. By providing a plurality of internal spin vanes within the waste gas inlet of a flare tip, the efficiency of combustion of waste gas can be increased.

This application claims the benefit of U.S. Provisional Patent Application No. 61/452,005, filed Mar. 11, 2011, and entitled “Flare Tip Having Internal Spin Vanes”. U.S. Provisional Patent Application No. 61/452,005, filed Mar. 11, 2011, is hereby incorporated by reference.

TECHNICAL FIELD

The disclosure relates generally to a flare tip for the burning and disposal of flammable waste gases and more particularly, to a flare tip including internal spin vanes.

BACKGROUND

Gas flares are commonly located at production facilities, refineries, processing plants, and the like for disposing of flammable waste gases and other flammable gas streams that are diverted due to venting requirements, shut-downs, upsets, and/or emergencies. Such flares are often operated in a smokeless or near smokeless manner, which can be largely achieved by making sure that the flammable gas to be discharged and burned (“flare gas”) is admixed with enough air to sufficiently oxidize the gas.

A typical flare apparatus includes a flare stack, which can extend high above the ground, and a flare tip mounted on the flare stack. An elevated flare tip is a device often used in industrial applications to burn combustible materials in an elevated location. Advanced flare tips use various methods in an attempt to provide sufficient oxygen in the combustion zone of the flare tip to help minimize the formation of smoke. In some larger flare tips, the exit of the flare tip is larger, and sometimes much larger, than the size of the waste gas riser that supplies the waste gas that includes the combustible material. Because the diameter of the flare tip is often larger than the flare riser, the waste gas velocity can be much higher in the center of the flare tip than at the perimeter of the flare tip. The higher flow of waste gas in the center of the flare tip can increase the oxygen requirements at the center of the flare tip, which can increase the propensity of the flare to smoke.

SUMMARY

The disclosure relates generally to a flare tip for the burning and disposal of combustible gases and more particularly, to a flare tip including internal spin vanes.

In an illustrative embodiment, a flare apparatus for burning and disposal of combustible waste gases is provided. The flare apparatus may include a flare tip having a waste gas conduit. The waste gas conduit may have a base portion defining a waste gas inlet and an upper portion defining a waste gas outlet. In some cases, the base portion of the waste gas conduit can have an outer diameter that is smaller than an outer diameter of the upper portion, but this is not required. The flare apparatus may include a plurality of spin vanes for inducing a spin in the waste gas entering the flare tip. In some instances, the plurality of spin vanes may be disposed within the base portion of the waste gas conduit. The spin vanes can be disposed at an angle relative to a longitudinal axis of the flare tip. The number, size, and angle of the spin vanes may vary depending upon a variety of factors including, for example, waste gas composition, waste gas flow rate, waste gas pressure, the available smokeless medium, the allowable heat and grade, as well as other factors. The flare apparatus may also include an outer shell defining a plenum surrounding the flare tip, if desired.

The above summary is not intended to describe each and every example or every implementation of the disclosure. The Description that follows more particularly exemplifies various illustrative embodiments.

BRIEF DESCRIPTION OF THE FIGURES

The following description should be read with reference to the drawings. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the disclosure. The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which:

FIG. 1 is a partial, cross-sectional view of a flare tip in accordance with an illustrative embodiment of the present disclosure;

FIG. 2 is a side, cross-sectional view of a flare tip in accordance with an illustrative embodiment of the present disclosure;

FIG. 3 is a detailed, plan view of a flare tip base including a plurality of internal spin vanes in accordance with an illustrative embodiment of the present disclosure;

FIG. 4 is an end, cross-sectional view of a flare tip in accordance with an illustrative embodiment of the present disclosure;

FIGS. 5A-5D show the burn profiles of a waste gas stream using a modified flare tip including spin vanes;

FIGS. 5E-5F show the velocity contours within a waste gas stream produced using the same modified flare tip used to produce the burn profiles of FIGS. 5A-5D.

FIGS. 6A-6D show the burn profiles of a waste gas stream using a flare tip including spin vanes and a twenty-four inch velocity seal;

FIGS. 6E-6F show the velocity contours within a waste gas stream produced using the same modified flare tip used to produce the burn profiles of FIGS. 6A-6D; and

FIGS. 6G-6H show the velocity contours within the waste gas stream measured just above the velocity seal of the same modified flare tip used to produce the burn profiles and velocity profiles of FIGS. 6A-6F.

DESCRIPTION

The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the disclosure. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized.

FIGS. 1-4 show various cross-sectional views of an illustrative flare apparatus 10. As shown in FIGS. 1 and 2, the flare apparatus 10 may include a flare tip 14 having a base portion 18 defining a waste gas inlet 22 and an upper portion 26 defining a waste gas outlet 30. In certain embodiments, such as shown in FIGS. 1 and 2, the base portion 18 has an outer diameter smaller than an outer diameter of the upper portion 26, but this is not required.

As best shown in FIG. 3, a plurality of spin vanes 36 may be disposed within, for example, the base portion 18. The spin vanes 36 may induce a spin on the waste gas entering the flare tip 14 through the waste gas inlet 22. The energy needed to produce the spin comes from the kinetic energy present in the flowing waste gas. In many instances, no additional equipment is necessary to induce a spin on the waste gas entering the flare tip 14.

In many flare tip designs, more oxygen for combustion is available near the perimeter of the flare tip 14 than is available near the center of the flare tip 14. When a spin is induced in the waste gas entering the flare tip 14, the resulting centrifugal action may distribute the waste gas more toward the outer edges or perimeter of the flare tip 14. By shifting waste gas flow closer to the perimeter of the flare tip 14, where more oxygen is often available, the propensity for the waste gas to smoke when burned may be reduced.

Flare tips are often customized depending upon the application, and it is contemplated that the number, size, and angle of the spin vanes 36 may vary. The number, size, and angle of the spin vanes 36 disposed within the flare tip 14 may vary depending upon a variety of factors including, for example: the waste gas composition, diameter of the waste gas inlet 22, waste gas flow velocity, waste gas pressure, the available smokeless medium, the allowable heat and grade, as well as other factors.

In general, the larger the diameter of the waste gas inlet 22, the larger the number and/or size of the spin vanes 36 may be used. Typically, the diameter of the waste gas inlet 22 can range from about 8 inches to about 72 inches, depending upon the application, but this is just an example range. Depending upon the diameter of the waste gas inlet 22 and the amount of spin needed to distribute the waste gas to the perimeter of the flare tip 14, the number of spin vanes 36 disposed within the base portion 18 of the flare tip 14 may range from, for example, 2 to 36 spin vanes. In other embodiments, the number of spin vanes 36 can range from 24 to 36 spin vanes, from 12 to 24 spin vanes, and from 2 to 12 spin vanes, or any other suitable range. In the illustrated embodiment shown in FIGS. 1-3, eight spin vanes 36 are utilized. The size of the spin vanes 36 can also be varied depending on, for example, the diameter of the waste gas inlet 22 and the number of spin vanes 36 provided. In some embodiments, the width of the spin vanes 36 can range from 1 inch to about 18 inches, but again, these are just examples. In other embodiments, the width of the spin vanes 36 can range from about 8 inches to about 18 inches, from about 4 to about 8 inches, and from about 1 inch to about 4 inches.

The angle relative to the longitudinal axis 40 (FIG. 2) at which each of the spin vanes 36 are disposed within the base portion 18 of the flare tip 14 can also vary, depending on the application. In certain embodiments, the angle of the spin vanes 36 relative to the longitudinal axis 40 of the flare tip 14 may be equal to or less than about 60° and more particularly, ranges from about 20° to about 60° or from about 20° to about 40°. In other embodiments, the angle of the spin vanes 36 relative to the longitudinal axis 40 of the flare tip 14 is about 30°. Thus, it is contemplated that the angle of the spin vanes may be any suitable value or within any suitable range. In some cases, it is contemplated that the angle of the spin vanes 36 may change or vary from the upstream end of the spin vanes 36 to the downstream end, while in other cases, the angle may be constant. In some cases, waste gas composition can also affect the angle, size and number of spin vanes 36 that are desired for a particular application.

As shown in FIGS. 1-4, the flare apparatus 10 can also include a one or more combustion air conduits 44 for supplying combustion air to the flare tip 14. In some embodiments, as illustrated, the combustion air conduits 44 may be disposed within and in fluid communication with the upper portion 26 of the flare tip 14. In some instances, spaces are provided between the combustion air conduits 44 to, for example, allow the waste gas to travel up and past the combustion air conduits 44. In some embodiments, the combustion air conduit(s) 44 may be provided external to, but still in fluid communication with the flare tip 14. The combustion air conduits 44 can be fabricated from, for example, carbon steel or stainless steel piping, and may be capable of delivering air and/or steam to the flare tip 14, depending upon the application.

In some instances, the flare apparatus 10 may include an outer shell 48 defining a plenum 52 surrounding the flare tip 14 (FIGS. 1 and 2), but this is not required. According to one embodiment, as illustrated, the outer shell 48 can include a generally cylindrical lower portion 52 and a frustoconical upper portion 56 defining an opening 60. In certain embodiments, such as shown in FIG. 1, the opening 60 of the upper portion 56 of the outer shell 48 can be elevated relative to the waste gas outlet 30 defined by the flare tip 14. In some cases, atmospheric air can be forced through the plenum 52 surrounding the flare tip 14.

Spin vanes, as discussed herein, may be combined with other tips of flare tip internal structures such as, for example, velocity seals.

EXAMPLES Example 1

A computational fluid dynamic study (CFD) of the combustion of a propane gas stream was conducted using a modified flare tip including five-inch wide internal spin vanes. The operating parameters utilized to conduct this study are provided in Table 1.

TABLE 1 Parameter Propane Flow 60,000 lbs/hr Propane Temp 100° F. Air Flow 100,000 ACFM Air Temp 100° F. Wind Speed/Direction 10 ft/sec left-right

FIGS. 5A-5D show the burn profiles of a combustion gas stream using the modified flare tip. FIGS. 5A-5B show the air volume fraction within the gas stream, and FIGS. 5C-5D show the volume fraction of propane within the combustion gas stream. FIGS. 5E-5F show the velocity contours within the gas stream produced using the modified flare tip.

The burn profiles shown in FIGS. 5A-5F exhibit improved velocity profiles when comparing the modified flare tip including the internal spin vanes to a flare tip without spin vanes (not shown). Additionally, the burn profiles shown in FIGS. 5A-5F show improved mixing between the waste gas (propane gas) and the surrounding atmosphere.

Example 2

A similar CFD study to that discussed in Example 1 was conducted using a modified flare tip including five-inch wide internal spin vanes and a twenty-four inch velocity seal. The operating parameters utilized to conduct the study are provided below in Table 2.

TABLE 2 Parameter Propane Flow 60,000 lbs/hr Propane Temp 100° F. Air Flow 100,000 ACFM Air Temp 100° F. Wind Speed/Direction 10 ft/sec left-right

FIGS. 6A-6D show the burn profiles of a combustion gas stream using the modified flare tip including a twenty-four inch velocity seal. FIGS. 6A-56B show the air volume fraction within the gas stream, and FIGS. 6C-6D show the volume fraction of propane within the combustion gas stream. FIGS. 6E-6H show the velocity contours within the gas stream produced using the modified flare tip including a twenty-four inch velocity seal.

Again, the burn profiles and velocity profiles shown in FIGS. 6A-6H show improved mixing between the waste gas (propane gas) and the surrounding atmosphere.

As a result of the CFD studies, it is believed that by providing internal spin vanes within the flare tip, the velocity profile within the flare tip is improved, improving mixing between the waste gas and the surrounding atmosphere.

The disclosure should not be considered limited to the particular examples described above. Various modifications, equivalent processes, as well as numerous structures to which the disclosure can be applicable will be readily apparent to those of skill in the art upon review of the instant specification. Other steps may be provided, or steps may be eliminated, from the described methods, and other components may be added to, or removed from, the described devices. Also, in the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 

1. A flare apparatus for burning and disposal of combustible waste gases, the flare apparatus comprising: a flare tip comprising a waste gas conduit having a base portion defining a waste gas inlet and an upper portion defining a waste gas outlet, the base portion having an outer diameter smaller than an outer diameter of the upper portion; and a plurality of spin vanes for inducing a spin on the waste gas entering the flare tip disposed within the base portion, the spin vanes disposed at an angle relative to a longitudinal axis of the flare tip.
 2. The flare apparatus according to claim 1, further comprising a plurality of combustion air conduits for supplying combustion air disposed within and in fluid communication with the upper portion of the flare tip.
 3. The flare apparatus according to claim 1, further comprising an outer shell defining a plenum surrounding the flare tip.
 4. The flare apparatus according to claim 1, wherein the flare tip is coupled to and in fluid communication with a flare stack.
 5. The flare apparatus according to claim 1, wherein the outer shell has a generally cylindrical lower portion and a frustoconical upper portion defining an opening wherein the opening of the upper portion of the outer shell is elevated relative to the waste gas outlet defined by the upper portion of the flare tip.
 6. The flare apparatus according to claim 1, wherein the angle of the spin vanes relative to the longitudinal axis of the flare tip ranges is less than about 60°.
 7. The flare apparatus according to claim 1, wherein the angle of the spin vanes relative to the longitudinal axis of the flare tip ranges from about 20° to about 60°.
 8. The flare apparatus according to claim 1, wherein the angle of the spin vanes relative to the longitudinal axis of the flare tip is about 30°.
 9. The flare apparatus according to claim 1, wherein the plurality of spin vanes comprises 2 to 36 spin vanes.
 10. The flare apparatus according to claim 1, wherein the plurality of spin vanes comprises 24 to 36 spin vanes.
 11. The flare apparatus according to claim 1, wherein the plurality of spin vanes comprises 12 to 24 spin vanes.
 12. The flare apparatus according to claim 1, wherein the plurality of spin vanes comprises 2 to 12 spin vanes.
 13. The flare apparatus according to claim 1, wherein a width of the spin vanes ranges from about 8 inches to about 18 inches.
 14. The flare apparatus according to claim 1, wherein a width of each of the spin vanes ranges from about 4 inches to about 8 inches.
 15. The flare apparatus according to claim 1, wherein a width of each of the spin vanes ranges from about 1 inch to about 4 inches.
 16. A flare apparatus having a flare tip and a number of distributing features for distributing a waste gas stream in the flare tip.
 17. A method comprising: receiving a waste gas flow; distributing the waste gas flow within a flare tip.
 18. The method of claim 17, wherein the distributing step includes inducing a spin in the waste gas flow. 